Cryptic diversity within two widespread diadromous freshwater fishes
(Teleostei: Galaxiidae)
Abstract
Aim Identification of taxonomically cryptic species is essential for the
effective conservation of biodiversity. Freshwater-limited organisms
tend to be genetically isolated by drainage boundaries, and thus may be
expected to show substantial cryptic phylogenetic and taxonomic
diversity. By comparison, populations of diadromous taxa, that migrate
between freshwater and marine environments, are expected to show less
genetic differentiation. Here we test for cryptic diversity in
Australasian populations (both diadromous and non-diadromous) of two
widespread Southern Hemisphere fish species. Location Throughout both
their Australian ranges (including Lord Howe Island) and localities in
New Zealand (including the Subantarctic Islands and Chatham Island).
Taxon Galaxias brevipinnis and Galaxias maculatus. Methods mtDNA and
nuclear markers were used to assess the presence of cryptic species and
to determine if differences in species ecology could influence the
degree of cryptic diversity. Results Both mtDNA and nuclear markers
reveal putative cryptic species within these taxa. The substantial
diversity detected within G. brevipinnis may be explained by its strong
climbing ability which allows it to form isolated inland populations. In
island populations, G. brevipinnis similarly show deeper genetic
divergence than those of G. maculatus, which may be explained by the
greater abundance of G. maculatus larvae in the sea allowing more
ongoing dispersal. Main conclusions Our study highlights that even
widespread, ‘high-dispersal’ species can harbour substantial cryptic
diversity and therefore warrant increased taxonomic and conservation
attention.